Hi,
I have found this discussion pretty interesting and entretaining. However I am surprised no to see any reference to Colombia within discussion. I know it is pretty late to keep discussing replacements on the original list but I know development is constant evolution and many versions can be released.
My proposal here is not to forget the first ibero-american republic founded, La Gran Colombia, which covers what we know today as Colombia, Venezuela, Ecuador and Panama. I think that either the early independent Mexican Empire and the Gran Colombia Republic were USA's biggest competitors within America during early 19th century which, along with the struggle for the control of Panama, worths some historic (and game fun) consideration.
I also agree with those who proposed the Kazakhs as a civ considering their strategic position and their persistence as a country nowadays.
By the way I offer whoever is involved in this mod my help with any data regarding Mexico, Central America or the Gran Colombia region. I have already sketched city lists for Mexico and Gran Colombia considering early and current importance.
Regards